Tuolumne Meadows Parking - FINAL Geotech Report_20200710.pdf

SUBMITTED TO:

Jacobs Engineering 707 17th Street Denver, Colorado 80202

BY:

Shannon & Wilson, Inc.

1321 Bannock St. Suite 200 Denver, Colorado 80204

(303) 325-3800 www.shannonwilson.com

GEOTECHNICAL DESIGN REPORT

CA NPS YOSE 17(4) & 941(1)

Tuolumne Meadows Parking

TUOLUMNE COUNTY, CALIFORNIA

July 2020

Shannon & Wilson No: 23-1-01458-070

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CONTENTS

1 Introduction

2 Project and Site Description

3 Field Explorations and Laboratory Testing

3.1 Subsurface Explorations

3.2 Laboratory Testing

3.3 Geophysics Surveys

4 Regional Geology and Subsurface Conditions

4.1 Regional Geology

4.2 Subsurface Conditions

4.3 Groundwater

5 Geologic Hazards

5.1 Seismic Hazards

5.2 Corrosion

6 Visitor Center and Visitor contact Station Parking Lots

7 Rockery Wall Design Recommendations

7.1 Seismic Design Parameters

7.2 Rockery Wall Design

7.2.1 Global Stability

7.2.2 Lateral Earth Pressures

7.2.3 Bearing Resistance

7.2.4 Sliding Resistance

7.2.5 Overturning

7.3 Wall Drainage

8 Construction and Materials Specifications

8.1 Excavation

8.2 Site Preparation

8.3 Temporary Excavation Slopes

8.4 Proof-rolling

8.5 Fill Placement and Compaction

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9 Closure

10 References

Exhibits Exhibit 7-1: Seismic Design Ground Motion Parameters Exhibit 7-2: Recommended Base Rock Width and Wall Heights Exhibit 7-3: Recommended Lateral Earth Pressure Design Parameters Exhibit 7-4: Recommended Base Rock Width and Wall Heights Exhibit 7-5: Recommended Parameters for Rockery Wall Design

Figures Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Figure 3: Recommended Surcharge Loading for Temporary and Permanent Walls

Appendices Appendix A: Subsurface Explorations Appendix B: Laboratory Test Results Appendix C: Geophysical Investigation Report Important Information

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1 INTRODUCTION

This report summarizes the results of our subsurface exploration and laboratory testing program and presents recommendations and construction considerations for the proposed Tuolumne Meadows Parking Project (the Project) in Tuolumne County, California. Our conclusions and recommendations in this report are based on:

The limitations of our approved scope, schedule, and budget described in our contract;

Our understanding of the Project and information provided by Jacobs;

Subsurface conditions observed in the borings at the time our explorations were completed; and

The results of testing performed on samples collected from the explorations.

The objective of our geotechnical studies was to provide recommendations and construction considerations, as presented herein, for the proposed Project. The authorized scope of services was based on this objective and this report should not be used for other purposes without Shannon & Wilson's review. If a service is not specifically indicated in this report, do not assume that it was performed.

2 PROJECT AND SITE DESCRIPTION

The Project is located within Yosemite National Park in Tuolumne County, California (Figure 1). The proposed project includes modifications to parking areas along Tioga Road within the Tuolumne Meadows area. Based on discussions with Jacobs, three sites are included in the project: the Visitor Center (Site 4), the Visitor Contact Station (Site 5), and the Dog Lake Trailhead (Site 11).

New parking lots are proposed at each location. Parking lot area construction will use a predetermined section of 4 inches of asphalt concrete pavement (ACP) over 6 inches of untreated aggregate base course (UTBC).

Based on preliminary plans provided by Jacobs, the new Dog Lake Trailhead parking area will include a rockery cut wall at the north side of the parking lot and a rockery fill wall at the south side of the parking lot. We understand that the cut wall will have a maximum wall height of 13.7 feet while the fill wall will have a maximum wall height of 9.3 feet.

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3 FIELD EXPLORATIONS AND LABORATORY TESTING

3.1 Subsurface Explorations

Shannon & Wilson conducted a field exploration program from October 23 through 25, 2018, to explore subsurface conditions at the Project locations. The subsurface exploration program consisted of drilling and sampling three borings at the Visitor Center (designated SW-01 through SW-03), three borings at the Visitor Contact Station (designated SW-04 through SW-06), and four borings at the Dog Lake Trailhead (designated SW-07 through SW-10), as shown in Figure 2. The borings were advanced to depths ranging from 1.5 feet to 30 feet below the ground surface. Due to the shallow depth to bedrock at the Visitor Center and the Visitor Contact Station, we were unable to install piezometers in any of the borings.

Appendix A presents a discussion of the drilling and sampling procedures used to complete the borings. Appendix A also presents the individual exploration logs and an explanation of the symbols and terminology used. Photographs of the rock core and drilling locations are also included in Appendix A.

3.2 Laboratory Testing

Geotechnical laboratory tests were completed on selected samples retrieved from the borings to estimate index and engineering properties. Laboratory testing included natural water content, grain size analysis, Atterberg limits, corrosion, and unconfined compressive strength. Laboratory test results and a discussion of the testing procedures are included in Appendix B. The natural water content, fines content, and Atterberg limits are also shown on the individual boring logs included in Appendix A.

3.3 Geophysics Surveys

A supplemental field exploration program included geophysical surveys performed on October 30, 2018 by Olson Engineering, Inc. (Olson) under subcontract to Shannon & Wilson. The objective of the survey was to map the depth to bedrock at the Visitor Contact Station and the Dog Lake Trailhead. Seismic Refraction Tomography (SRT) was used to acquire data at the two locations.

The geophysical survey consisted of two seismic refraction survey lines each at the Visitor Contact Station and the Dog Lake Trailhead. The results, description of data acquisition, and analytical methods employed by Olson are presented in the enclosed Geophysical Investigation Report included as Appendix C.

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4 REGIONAL GEOLOGY AND SUBSURFACE

CONDITIONS

4.1 Regional Geology

The project is located within the boundary of the Yosemite National Park, on the western slope of the central Sierra Nevada batholith. The Sierra Nevada batholith is an uplifted tectonic block that has formed between the active Owens Valley Fault zone to the east and the Great Valley on the west (Bateman and others, 1983). The Sierra Nevada batholith is primarily composed of intrusive or plutonic rocks with near-surface secondary rock types composed of metamorphic, volcanic, and sedimentary rock roof pendants. Overlying the rock within the Tuolumne Valley area and north of the project site are relatively young glacial deposits.

At the Project site, published mapping shows that the Cathedral Peak Granodiorite underlies the Project limits. The formation is described as tonalite, granodiorite and quartz diorite that is well-foliated, medium grained, and equigranular; tonalite and calcic granodiorite contain abundant mafic inclusions.

4.2 Subsurface Conditions

Borings SW-01 through SW-03 were drilled at the proposed Visitor Center and encountered approximately 12 inches of forest duff and topsoil overlying loose to medium dense silty sand. At depths ranging from 2.5 to 4 feet below ground, surface auger refusal was encountered on granodiorite bedrock.

At the Visitor Contact Station, borings SW-04 through SW-06 encountered approximately 12 inches of forest duff and topsoil. Loose to very dense, silty sand was then encountered overlying bedrock. Auger refusal was encountered on granodiorite bedrock at depths ranging from 1.5 to 4.3 feet below ground surface.

Borings SW-07 through SW-10, were completed at the Dog Lake Trailhead, and encountered approximately 12 inches of forest duff and topsoil. Borings SW-07 and SW-08 were completed near the proposed cut wall and encountered medium dense to very dense, silty sand to depths of approximately 6 and 9 feet, respectively, where wireline rock core drilling techniques were then used. Granodiorite was encountered to the termination depth of both borings at 30 feet. Underlying the forest duff and topsoil, borings SW-09 and SW-10 encountered loose to very dense, silty sand to a depth of approximately 6 to 7 feet, where auger refusal was encountered.

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Our observations are specific to the locations, depths, and dates noted on the exploration logs in Appendix A and may not be applicable to all areas of the site. There is no amount of explorations or laboratory testing that can precisely predict the characteristics, quality, or distribution of subsurface conditions at every location throughout the site. Variations in the subsurface conditions may occur between and below the borings. Also, the passage of time or intervening causes (natural and manmade) may result in changes to the conditions of the site and subsurface conditions.

4.3 Groundwater

Groundwater was not encountered in any of our borings; however, fluctuations of groundwater levels at the site are possible and will depend on many factors, including seasonal variations, local precipitation, and flood events. Because we were unable to install piezometers in any of the borings at the Visitor Center and the Visitor Contact Station, long-term groundwater levels are not available.

5 GEOLOGIC HAZARDS

5.1 Seismic Hazards

The California Geological Survey (CGS) and United State Geological Survey (USGS) have mapped faults and identified fault activity in the region (Jennings and Bryant, 2010; USGS, 2016). The closest mapped Quaternary faults is the Silver Lake Fault, located approximately 10 miles east from the Tuolumne Meadows area. The Silver Lake Fault system is indicated by the USGS as Quaternary active.

The Alquist-Priolo Earthquake Fault Zoning Act produced 1:2000 scale maps of active faults as determined by the State Geologist for the CGS. Based on these maps, the immediate Project site is not located within an Alquist-Priolo Earthquake Fault Zone and is not underlain by known active faults (Jennings and Bryant, 2010). Because no recognized active faults are present at the immediate Project site, the potential for fault surface rupture at the site is low, in our opinion.

Soil liquefaction is a phenomenon in which pore pressure in loose, saturated, granular soil increases during ground shaking to a level near the initial effective stress, resulting in a reduction of shear strength of the soil. As a result of this reduction in shear strength during liquefaction, ground settlement, lateral spreading (ground movement on very gentle slopes), and landslides may occur. Liquefaction potential is greatest where loose granular soil (sand and non-plastic silt) is present below groundwater. Liquefaction potential decreases as the

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23-1-01458-070 July 2020 fines (clay and silt) content of soil increase and increases as ground shaking increases.

Because of the reduced soil strengths, vertical and lateral foundation resistance may also be reduced.

Based on our subsurface explorations, the residual soils over shallow bedrock are typically medium dense to dense and the subsurface explorations did not encounter groundwater.

Therefore, we consider the potential for liquefaction at the site to be low.

5.2 Corrosion

The soil materials can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, samples of silty sand from each parking lot were tested for pH, resistivity, water soluble sulfates, and chlorides. The results are presented in Table B-1 in Appendix B.

The resistivity measured in the samples was greater than 66,000 ohm-centimeter (ohm-cm).

Based on correlations developed by Roberge (2012), these values suggest an essentially noncorrosive subsurface.

The concentration of water-soluble sulfates measured in the samples was 0.01 percent or less by weight (100 parts per million (ppm)). Based on classifications as defined by ACI-318-14 (ACI, 2014), these test results suggest a negligible degree of sulfate attack on concrete exposed to site soils (exposure class S0).

6 VISITOR CENTER AND VISITOR CONTACT STATION

PARKING LOTS

Shallow bedrock was encountered throughout our borings completed at the Visitor Center and Visitor Contact Station parking lots. As discussed in Section 4.2, bedrock was encountered at depths ranging from 2.5 to 4 feet below ground surface at the Visitor Center parking lot. At the Visitor Contact Station parking lot, borings SW-04 through SW-06 encountered auger refusal at depths ranging from 1.5 to 4.3 feet below ground surface.

These shallow bedrock depths were confirmed by the geophysics completed at each parking lot. Refer to Appendix C for a detailed report of the geophysics completed at the project site.

We understand that shallow groundwater and standing water is often present in the Tuolumne Meadows area in the spring when seasonally heavy snowfall is typical. It is believed that rapid snow melt and runoff combined with shallow bedrock creates the

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23-1-01458-070 July 2020 seasonal groundwater conditions observed by the project team during spring site visits. As indicated in Section 4.3, groundwater was not encountered in any of our borings and evidence of shallow groundwater was not apparent during summer and fall site visits.

Subsurface drains may be of value, particularly along the uphill side of pavement areas to reduce the potential for shallow groundwater flow to collect under paved areas.

Pavement design was not completed under this scope of work. We understand that a structural section of 4 inches ACP over 6 inches of UTBC will be used for all parking lots.

7 ROCKERY WALL DESIGN RECOMMENDATIONS

The rockery wall design was completed in accordance with the Rockery Design and Construction Guidelines, Publication No. FHWA-CFL/TD-06-006, (Rockery Guidelines) developed by Mack and others (2006) and AASHTO LRFD Bridge Design Specifications Eighth Edition, 2017 (AASHTO). Our analyses assumed that this project is constructed according to FP-14 U.S. Customary Units (FHWA, 2014) construction standards. The Rockery Guidelines provide factors of safety using allowable stress design (ASD) methods.

We evaluated the global stability, lateral earth pressures, bearing resistance, sliding resistance, and overturning of the proposed rockery walls, considering a proposed critical section of the wall based on the foreslope and backslope, wall height, and subsurface conditions.

The proposed rockery walls include both a cut wall and fill wall. The cut wall is proposed at the north end of the parking lot with a maximum wall height of 13.7 feet. The fill wall is proposed at the south end of the parking lot with a maximum wall height of 9.3 feet. Based on our borings, we anticipate that the cut wall will be founded near the granodiorite bedrock elevation. We anticipate that the fill wall will be founded in the silty sand overburden.

7.1 Seismic Design Parameters

Using the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO, 2020) criteria, and based on subsurface conditions encountered in our borings at the proposed wall locations (assuming that similar conditions are present from the maximum depth of our boring to a depth of 100 feet), Site Class C is recommended for the proposed wall structures.

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Ground motion parameters were determined for the project site using the USGS AASHTO 2009 Web Service Documentation Web Application (USGS, 2009) and procedures recommended by AASHTO (2020). Exhibit 5-1 presents recommended seismic design ground motion parameters.

Exhibit 7-1: Seismic Design Ground Motion Parameters

Design Parameter Value Peak Ground Acceleration 1 (PGAB) 0.315 g

Site Class C

Short-period Spectral Acceleration, SS 0.772 g

Long-period Spectral Acceleration, S1 0.252 g

Site Factor, Fpga 1.085

Site Factor, Fa 1.091

Site Factor, Fv 1.548

Peak Design Spectral Acceleration, AS 0.342 g

Short-period Design Spectral Acceleration, SDS 0.842 g

Long-period Design Spectral Acceleration, SD1 0.390 g

T0 0.093 sec.

TS 0.436 sec.

NOTES:

PGAB = peak ground acceleration for a site underlain by Site Class B soil (soft rock) g = gravity; sec. = seconds

We evaluated seismic wall stability using pseudo-static analysis with an applied horizontal seismic coefficient (kh). In developing the appropriate value of kh, we considered the following from the Rockery Guidelines: "Published values of kh range between 0.05 and 0.2, although some researchers have suggested ranges between 0.3 to 0.5 times the site PGA. For seismic performance categories B, C, and D, AASHTO recommends kh be taken as 0.5A for gravity retaining structures." We also considered guidance from the California Department of Transportation (Caltrans), which recommends using kh equal to one-third the design PGA, but not greater than 0.2 g (Caltrans, 2016) for pseudo-static slope stability.

Considering the above, and that the rockeries support a parking lot, we used a kh value of one-third the design PGA, or 0.11g, in our design. If a higher value of kh is desired by CFLHD, our analyses indicate that an unreinforced rockery wall will not be feasible.

7.2 Rockery Wall Design

In general, we used the Rockery Guidelines for our design. The following sections present design parameters and methodologies used for design of the rockery walls.

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7.2.1 Global Stability

The global stability of the proposed rockery walls considers the depth of the silty sand and granodiorite, steepness of the backslope, and height of the cut and fill walls. Above the cut walls, the existing ground surface slopes at about 22 degrees (approximately 1V:2.5H). The maximum proposed wall height will be 13.7 feet. The fill walls will include an essentially flat backslope for the parking lot and a fore slope of approximately 1V:4.5H. To provide static and seismic factor of safety values equal to 1.5 and 1.1, respectively (which are the minimum values provided in the Rockery Guidelines), the base rock widths in Exhibit 7-1 will need to be satisfied.

Exhibit 7-2: Recommended Base Rock Width and Wall Heights

Base Rock Width (feet)

Wall Height (feet)

4.0 < 8

4.5 8 - 9.5

5.0 9.5 - 10.5

5.5 10.5 - 11.5

6.0 11.5 - 13.7 (max height) max = maximum

In accordance with Rockery Guidelines we checked global stability with failure planes through the rockery facing using an anisotropic function with a horizontal friction angle of 29 degrees to represent the frictional interface between the blocks.

7.2.2 Lateral Earth Pressures

The rockeries will retain native, silty sand or backfill soil. We recommend that backfill soil consist of Backfill Material (FP-14 704.03). Both native, silty sand and Backfill Material will have similar properties as presented in Exhibit 7-3. These parameters do not include hydrostatic pressure related to accumulation of water in the backfill. We obtained the lateral earth pressure coefficient KA used for design from the Rockery Guidelines and the input parameters presented in Exhibit 7-3.

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Exhibit 7-3: Recommended Lateral Earth Pressure Design Parameters

Design Parameter Design Value

Retained Material Native Recompacted Silty Sand or Import Backfill Material 1

Total Unit Weight (pcf) 125

Effective Friction Angle (degrees) 34

Cohesion (psf) 0

Seismic horizontal Acceleration Coefficient, kh 2 0.11

Fill Walls Cut Walls

Backslope (degrees) 0 22

NOTES:

Surcharge loading should be applied as recommended in Figure 3.

See Section 7.1.

pcf = pounds per cubic foot; psf = pounds per square foot; H = height of wall in feet

7.2.3 Bearing Resistance

The rockery walls will generally be founded on silty sand or granodiorite bedrock. There is potential for the silty sand material to be loose in areas at the proposed bearing elevation for the fill wall. To provide adequate subgrade support and to reduce potential settlement and differential settlement associated with such soils, we recommend over-excavating a minimum depth of 3 feet below the existing ground surface for the fill wall. In the cut walls we anticipate that the excavation to the proposed base rock elevation will expose dense silty sands or granodiorite. The base rock should be embedded a minimum of 2 feet below final grades. Refer to Exhibit 7-4 for allowable bearing resistance for variable base rock widths.

The bearing resistance values assumes support on medium dense or dense, silty sand. In accordance with the Rockery Guidelines, an ASD factor of safety of 3 is included in the allowable bearing resistance values.

Exhibit 7-4: Recommended Base Rock Width and Wall Heights

Base Rock Width Allowable Bearing Resistance 1

4.0 ft 3,300 psf

4.5 ft 3,700 psf

5.0 ft 4,100 psf

5.5 ft 4,500 psf

6.0 ft 4,950 psf

NOTES:

Assumes a minimum embedment depth of 2 feet.

ft = feet; psf = pounds per square feet

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Based on the proposed wall heights, we anticipate up to 1 inch of total settlement with the majority of settlement occurring during construction of the wall.

To provide uniform support for the rockery walls, we recommend placing a minimum of 12 inches of Foundation Fill (FP-14 704.01) on the subgrade beneath the wall before placing the base rock layer. This layer should extend 12 inches laterally on each side of the base rock width and be compacted to 95 percent relative compaction as determined by AASHTO T180.

7.2.4 Sliding Resistance

The resistance of the rockery walls to sliding is provided by friction along the base of the wall. Design parameters presented in Exhibit 7-5 were used in accordance with Rockery Guidelines to calculate sliding resistance and meet minimum Factors of Safety.

Exhibit 7-5: Recommended Parameters for Rockery Wall Design

Design Parameters Recommended Value

Unit Weight of Rockery (pcf) 150

Soil Friction Angle (degrees) 34

Ultimate Coefficient of Friction for Rock-Structural Fill 0.7

Factor of Safety for Sliding, Static 1.5

Factor of Safety for Sliding, Seismic 1.1

NOTES:

pcf = pounds per cubic foot

7.2.5 Overturning

Rockery Guidelines were used to calculate the Factors of Safety against overturning for the rockery walls under static and seismic loading. The overturning moments takes into account the lateral earth pressure forces and surcharge loading. The minimum factor of safety for static and seismic loading conditions required for design are 2.0 and 1.5, respectively.

7.3 Wall Drainage

Based on conditions encountered in the subsurface explorations, we do not anticipate the presence of groundwater near the base of the proposed rockery walls. Nevertheless, surface water can make its way into the backfill, regardless of the permeability of the material.

Therefore, we recommend providing drainage measures that reduce the potential for water to accumulate in the backfill and for hydrostatic pressures to act on the wall. A minimum of 12 inches of Granular Rock Backdrain material (FP-14 703.17) should be provided behind

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23-1-01458-070 July 2020 the wall to reduce the potential for the buildup of pore water pressure. The final drainage measures should collect water from the base of the wall and not allow water to collect in a bathtub-type situation.

8 CONSTRUCTION AND MATERIALS SPECIFICATIONS

The applicability of the design parameters is contingent on good construction practice. Poor construction techniques may alter conditions from those upon which our recommendations are based, and therefore result in poor performance. Our analyses assumed that this project is constructed according to FP-14 U.S. Customary Units (FHWA, 2014) construction standards. The following sections provide additional construction considerations for this project.

8.1 Excavation

The overburden soils can likely be excavated using conventional excavating equipment, such as a rubber-tired backhoe or tracked hydraulic excavator. Based on the proposed elevations of the rockery walls, we anticipate that the base rock may be below the granodiorite bedrock elevation.

Where excavations are required in the granitic bedrock, we anticipate blasting will be required. Unconfined compressive rock strengths encountered in borings SW-07 and SW-08 were 7,251 and 1,313 pounds per square inch, respectively. Rock blasting should be performed in accordance with FP-14 Section 205.

8.2 Site Preparation

Prior to site grading, surface vegetation and surficial topsoil containing organics should be removed. The depth of this removal is expected to be approximately 12 inches. Trees or shrubs to be removed should include the entire rootball and all roots larger than ½ an-inch-in diameter. This may require laborers handpicking the roots from the subsurface soils prior to compaction. Deleterious materials and vegetation should be disposed offsite.

In addition, construction areas should be cleared to a depth necessary to remove all surface and subsurface structures associated with current development of the site, including underground utilities and any other deleterious materials. Topsoil and organic rich soils can be re-used in landscape areas once walls and grading are constructed with on-site silty sands or imported granular materials.

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As discussed in Section 6, surficial runoff and groundwater is likely at the project site.

Construction timing should consider and account for the seasonal groundwater concerns.

8.3 Temporary Excavation Slopes

The safe slope for the excavation of subsurface materials depends on many factors, including: (a) the presence of groundwater; (b) the type, density, and shear strength of the subsurface materials; (c) the depth of excavation; (d) the presence of adjacent facilities;

(e) surcharge loading adjacent to the excavation (including excavated material, existing dead or live loads, and construction equipment); and (f) time of construction. Considering these factors, unshored, temporary excavation slopes may be possible in areas around the site.

For cost estimating and planning purposes only, we recommend assuming temporary excavations be sloped at 1H:1V in the overburden soil. These temporary excavation slopes assume no construction loading at the crest of the slope. If groundwater is seeping into the excavation, flatter slopes may be required.

Consistent with conventional practice, the contract documents should require the Contractor to be responsible for the actual temporary excavation slopes, including methods, sequence, and schedule of construction. The Contractor is able to observe the nature and conditions of the subsurface materials encountered and should evaluate the factors discussed above. If instability is observed, slopes should be flattened or shored. In this regard, we recommend that unshored, temporary excavation slopes be monitored closely for seeping water entering the excavation. All excavations should be accomplished in accordance with local, state, and federal safety regulations.

8.4 Proof-rolling

Proper subgrade preparation is required for structural support of pavement and rockery walls. After excavation to the required depth, the subgrade should be scarified a minimum of 8 inches, moisture treated and compacted, and proof rolled with a fully loaded, tandem-axle 10-yard dump truck or equivalent. Any areas that are delineated to be loose or yielding during proof-rolling should be removed until dense and unyielding subgrade is exposed.

8.5 Fill Placement and Compaction

Silty sand onsite materials excavated throughout the Project may be used as site fill. This material may also be used as wall backfill if the material meets the minimum requirements of FP-14 Backfill Material. Based on our laboratory testing, the overburden materials

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23-1-01458-070 July 2020 encountered at the rockery wall locations will be suitable for use as backfill. Import fill for rockery wall backfill should meet the requirements of Backfill Material (FP-14 704.03).

All fill and backfill should be compacted to a dense/firm and unyielding condition as specified in accordance with FP-14 Section 200. All fill should be moisture conditioned within 2 percentage points of the optimum moisture content and to at least 95 percent of the maximum dry density as determined by the appropriate Proctor in accordance with FP-14 Section 200.

Fill and backfill should be placed in maximum 6-inch-thick lifts when using heavy compaction equipment. The lift thickness should be reduced to 4 inches when using small compaction equipment for backfilling against rockery walls.

9 CLOSURE

This report has been prepared for the exclusive use of Jacobs and Central Federal Lands Highway Division for the purpose of providing geotechnical design recommendations for the Tuolumne Meadows Parking project. This geotechnical design report should not be used without our approval if any of the following occurs:

Assumptions stated in this report have changed.

Project details change or new information becomes available such that our analyses and recommendations may be affected.

A substantial period of time has passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses and recommendations.

Within the limitations of scope, schedule, and budget, the analyses, conclusions, and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical and geological principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

Shannon & Wilson, Inc. has prepared “Important Information about Your Geotechnical Report” to assist you and others in understanding the use and limitations of our reports.

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10 REFERENCES

American Concrete Institute (ACI), 2014, Building code requirements for structural concrete and commentary, Farmington Hills, Michigan, ACI 318-14.

American Association of State Highway and Transportation Officials, 2020, AASHTO LRFD bridge design specifications, Customary U.S. units, 9th edition: Washington, D.C., American Association of State Highway and Transportation Officials.

Bateman, P.C., Kistler, R.W., Peck, D.L., and Busacca, Alan, 1983, Geologic map of the Tuolumne Meadows quadrangle, Yosemite National Park, California: U.S.

Geological Survey, Geologic Quadrangle Map GQ-1570, scale 1:62,500.

California Department of Transportation (CalTrans), 2016, Highway Design Manual 6th Edition. Available from: http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm

Jennings, C., and Bryant, W., 2010, 150th Anniversary fault activity map of California:

California Geological Survey Map No. 6, scale 1:750,000.

Mack, D.A., Sanders, S.H., Millhone, W.L., Flippin, R.L., and Kennedy, D.G., 2006, Rockery design and construction guidelines: FHWA-CFL/TD-06-006, 178 p.

Roberge, P.R., 2012, Handbook of corrosion engineering, Second Edition: McGraw-Hill, New York, New York.

U.S. Department of Transportation, Federal Highway Administration, 2014, Federal Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 English Units: U.S. Department of Transportation and Federal Highway Administration, available from http://flh.fhwa.dot.gov/resources/pse/specs/.

U.S. Geological Survey (USGS) AASHTO 2009 Web Service Documentation Web Application (USGS, 2009). Available from:

https://earthquake.usgs.gov/ws/designmaps/

U.S. Geological Survey (and California Geological Survey), 2016, Quaternary fault and fold database for the United States, from USGS web site:

http//earthquakes.usgs.gov/regional/qfaults/.

http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm https://earthquake.usgs.gov/ws/designmaps/

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VICINITY MAP

FIG. 1

CA NPS YOSE 17(4) & 941(1)

Tuolumne Meadows Parking

Tuolumne County, California

July 2020

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

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Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

Approximate Scale in Feet

1000 2000

California

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Figure 2 - Sheet 2

Site 5 - Visitor Contact Station

Figure 2 - Sheet 3

Site 11 - Dog Lake Trailhead

Figure 2 - Sheet 1

Site 4 - Visitor Center

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M e a d o w s Lodge

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Tuolumne Meadows Parking

Tuolumne County, California

July 2020

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

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M e a d o w s

P a r k i n g D r a f t i n g F i g

F d t e t h o r r d d

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

Approximate Scale in Feet

50 100

SITE AND EXPLORATION PLAN

FIG. 2

Sheet 1 of 3

LEGEND

Boring Designation and

Approximate Location

SW-01

SW-03

SW-02

SW-01

Tioga Road

Visitor Center

Proposed Visitor

Center Parking Lot

AutoCAD SHX Text

ELECT J-BOX

AutoCAD SHX Text

ELECT J-BOX

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ELECT J-BOX

AutoCAD SHX Text

EP

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EP

AutoCAD SHX Text

EP

AutoCAD SHX Text

EP

AutoCAD SHX Text

6"DIP

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6"DIP

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4"DIP

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4"DIP

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6"DIP

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6"DIP

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

F i l e

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D

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J a c o b s

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T u o l u m n e

M e a d o w s

P a r k i n g D r a f t i n g F i g

F d t e t h o r r d d

SITE AND EXPLORATION PLAN

FIG. 2

Sheet 2 of 3

CA NPS YOSE 17(4) & 941(1)

Tuolumne Meadows Parking

Tuolumne County, California

July 2020

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

Approximate Scale in Feet

40 80

LEGEND

Boring Designation and

Approximate Location

SW-01

SW-05

SW-04

SW-06

Tioga Road

Proposed Visitor

Contact Station

Parking Lot

To Visitor Center

AutoCAD SHX Text

10" DI S

10" DI S

SHANNON & WILSON, INC.

F i l e

I E

F

D

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J a c o b s

C

F L

T u o l u m n e

M e a d o w s

P a r k i n g D r a f t i n g F i g

F d t e t h o r r d d

SITE AND EXPLORATION PLAN

FIG. 2

Sheet 3 of 3

CA NPS YOSE 17(4) & 941(1)

Tuolumne Meadows Parking

Tuolumne County, California

July 2020

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

Approximate Scale in Feet

40 80

LEGEND

Boring Designation and

Approximate Location

SW-01

SW-07

SW-09

SW-10

T u o l u m n e

M e a d o w s

L o d g e

R o a d

SW-08

T

T i o

R a d

Proposed Dog

Lake Trailhead

Parking Lot

Proposed Cut Wall

Proposed Fill Wall

AutoCAD SHX Text

10" DI S

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10" DI S

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10" DI S

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10" DI S

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10" DI S

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10" DI S

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10" DI S

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10" DI S

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10" DI S

10" DI S

For m ≤ 0.4: s H

= 0.28 (psf) (see Note 3)

F i l e

I E

F

D

E N s

J a c o b s

C

F L

T u o l u m n e

M e a d o w s

P a r k i n g D r a f t i n g F i g

F i g u r e

T y p

S u r c h a r g e d t e t h o r r d d

W a l l

PLAN VIEW

2.0 q

1.5

D e p t h

F a c t o r

Z

B

1.0

0.0

0.5

W a l l

Z

Wall Line

UNIFORM SURCHARGE

a b

EARTH BERM

(see Note 4)

Note:

H z=nH

Bottom of

Excavation x = mH

Point Load in Pounds s H

(psf)

ELEVATION VIEW

x = mH

H

Bottom of

Excavation

W a l l z=nH s H

(psf)

Line Load in

Pounds/Foot

B) LATERAL PRESSURE DUE TO LINE LOAD

i.e. NARROW CONTINUOUS FOOTING

PARALLEL TO WALL

C) LATERAL PRESSURE DUE TO STRIP LOAD

W a l l

W a l l

W a l l

A) LATERAL PRESSURE DUE TO POINT LOAD

i.e. SMALL ISOLATED FOOTING OR WHEEL LOAD y

D) LATERAL PRESSURE DUE TO EARTH BERM

OR UNIFORM SURCHARGE

Bottom of

Excavation

Bottom of

Excavation

E) LATERAL PRESSURE DUE

TO ADJACENT FOOTING

(see Notes 5 and 6)

0 0.5 1.0

L

B

NOTES

Figures are not drawn to scale.

Applicable surcharge pressures should be added to appropriate temporary and permanent wall lateral earth and water pressure.

If point or line loads are close to the back of the wall such that m £ 0.4, it may be more appropriate to model the actual load distribution (i.e., Detail E) or use more rigorous analysis methods.

See text for recommended K values.

The stress is estimated on the back of the wall at the center of the length, L, of loading.

The estimated stress is based on a Poisson's ratio of 0.5.

W a l l

Bearing

Pressure q (psf)

1.

2.

3.

4.

5.

6.

I p

, Influence Factor s H

= 2(I p

) q s

Lateral Footing

Pressure on Wall

(derived from NAVFAC DM 7.02, 1986; and Sandhu, Earth Pressure on Walls Due to Surcharge, 1974)

(derived from Poulos and Davis, Elastic Solutions for

Soil and Rock Mechanics, 1974; and Terzaghi and

Peck, Soil Mechanics in Engineering Practice, 1967)

(NAVFAC DM 7.02, 1986)

(derived from Fang, Foundation

Engineering Handbook, 1991)

(NAVFAC DM 7.2, 1986)

Point Load in Pounds g = Unit Weight of Earth Berm

Bearing

Pressure

Earth

Berm s H

= Lateral Pressure in radians

ELEVATION VIEW

(see Note 3)

(see Note 3) q s

L

2B

Q p

H n

(0.16 + n

For m > 0.4: s H

= 1.77 (psf)

Q p

H m n

(m

+ n

Q p s H s'

H

= s H cos

(1.1q) (psf) s'

H s'

H

For m ≤ 0.4: s H

= 0.20 (psf) (see Note 3)

Q l

H n

(0.16 + n

For m > 0.4: s H

= 1.28 (psf)

Q l

H m n

(m

+ n

Q l

Q p y ≤ 33°

H s

≤ 15 Feet

(K)(g)(H s s H

H s s H

= (K)q s

(see Note 4) q s

(psf) s H

= (b - sin b cos2a) (psf)

2q p

L

= 0.25

= 0.5

= 1 s H

L

2B

L

2B

L

2B

RECOMMENDED SURCHARGE

LOADING FOR TEMPORARY AND

PERMANENT WALLS

FIG. 3

23-1-01458-070July 2020

CA NPS YOSE 17(4) & 941(1)

Tuolumne County, California

7/9/2020-23-1-01458-070_AA.docx A-i

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Appendix A: Subsurface Explorations

Appendix A

Subsurface Explorations

A.1 Introduction ........................................................................................................................... A-1

A.2 Explorations ........................................................................................................................... A-1

A.2.1 Methodology ............................................................................................................. A-1

A.2.2 Soil and Rock Classification System ...................................................................... A-1

A.2.3 Standard Penetration Test (SPT) ............................................................................ A-2

A.2.4 Rock Core Sampling ................................................................................................ A-2

Figures Figure A-1: Soil Description and Log Key Figure A-2: Rock Classification and Log Key Figure A-3: Log of Boring SW-01 Figure A-4: Log of Boring SW-02 Figure A-5: Log of Boring SW-03 Figure A-6: Log of Boring SW-04 Figure A-7: Log of Boring SW-05 Figure A-8: Log of Boring SW-06 Figure A-9: Log of Boring SW-07 Figure A-10: Log of Boring SW-08 Figure A-11: Log of Boring SW-09 Figure A-12: Log of Boring SW-10 Figure A-13: Rock Core Photographs, Boring SW-07 Figure A-14: Rock Core Photographs, Boring SW-08 Figure A-15: Exploration Photographs

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A.1 INTRODUCTION

The field exploration program for the proposed improvements consisted of drilling and sampling ten geotechnical borings from October 23 through 25, 2018. A representative from Shannon & Wilson observed the drilling and sampling operations, retrieved representative samples for field classification and laboratory testing, and prepared descriptive field logs of the borings. The methods used to conduct the field exploration program are described below.

A.2 EXPLORATIONS

A.2.1 Methodology

The drilling was coordinated (including subcontractor coordination and utility locates) and observed by our field representatives. Individual boring logs are presented on Figures A-3 through A-12. These exploration logs represent our interpretation of the subsurface conditions encountered at the time of drilling and the results of laboratory testing. The location of each boring (Figure 2) was measured relative to existing features or with a recreational-grade handheld GPS at the site and should be considered accurate to the degree implied by the method used.

The borings were drilled by Woodward Drilling, Inc. of Rio Vista, California, under subcontract to Shannon & Wilson, using a truck-mounted B57 track rig. The borings were advanced with hollow stem auger drilling techniques. Borings SW-07 and SW-08 were advanced using wireline rock coring through bedrock to termination. Groundwater was not encountered in any of the borings. Each boring was backfilled with cuttings generated during drilling. Exploration photographs are presented on Figure A-15.

A.2.2 Soil and Rock Classification System

During drilling, the Shannon & Wilson representative collected soil/rock samples and prepared a field log of each boring. Soil classifications were based on American Society for Testing and Materials International (ASTM) Designation: D2487, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), and ASTM Designation: D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). The system is referred to as the Unified Soil Classification System and is summarized in Figure A-1.

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The Shannon & Wilson representative classified rock samples in general accordance with the International Society of Rock Mechanics (ISRM) classification method. According to this system, rocks are classified based on the stratigraphic structure, rock strength, degree of weathering, and other properties. The rock classification system is summarized in Figure A- 2.

A.2.3 Standard Penetration Test (SPT)

Disturbed samples were obtained in general accordance with the Standard Penetration Test (SPT) ASTM Designation: D1586. The SPT consists of driving a 2-inch outside diameter (O.D.), 1.375-inch inside diameter split-spoon sampler a distance of 18 inches with a 140-pound hammer free-falling a distance of 30 inches. An automatic hammer system was used to advance the samplers. During sampling, the Shannon & Wilson field representative recorded the number of blows for each 6-inch increment of penetration and summed the blow counts for the last two 6-inch increments. This sum is recorded as the penetration resistance number, or N-value. If high penetration resistance prevented driving the total length of the sampler, the Shannon & Wilson field representative recorded the partial penetration depth and blow count. The N-values provide a means for evaluating the relative density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine-grained) soils (see Figure A-1). The N-values are shown on the individual boring logs. Representative portions of the split-spoon sample obtained in conjunction with the SPT were placed in plastic jars and transported to our laboratory.

A.2.4 Rock Core Sampling

Rock samples were also collected using NQ double tube wireline coring methods (1.75-inch nominal diameter rock core) in borings SW-07 and SW-08. During coring, cuttings were removed from the borehole by circulating water down through the drill rods and back up the annulus of the boring. Water for coring was pumped from truck-mounted storage tanks or recirculated using a settlement trough. Core runs were approximately 5 feet in length. Percent recovery and rock quality designation (RQD) values are shown in the boring log where coring was completed. Percent recovery is the ratio of the length of recovered core to the total length of the core run. RQD is the ratio, expressed as a percent, of the sum of the length of intact core pieces greater than 4 inches long in a run to the total length of the core run. Following drilling, the core was logged by the Shannon & Wilson field representative, then stored in cardboard core boxes and transported to the Shannon & Wilson laboratory. Photographs of the core are presented in Figure A-13 and A-14.

Tuolumne County, California

23-1-01458-070July 2020

COBBLES

GRAVEL

FINES

SAND

Sheet 1 of 3

S&W INORGANIC SOIL CONSTITUENT DEFINITIONS

CONSTITUENT2

COHESIONLESS SOILS

Silt, Lean Clay, Elastic Silt, or

Fat Clay 3

PERCENTAGES TERMS 1, 2

Trace

Few

Little

Some

Mostly

WELL AND BACKFILL SYMBOLS

Bentonite Cement Grout

Bentonite Grout

Bentonite Chips

Silica Sand

Perforated or Screened Casing

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Absence of moisture, dusty, dry to the touch

Damp but no visible water

Visible free water, from below water table

FIG. A-1

Shannon & Wilson, Inc. (S&W), uses a soil identification system modified from the Unified Soil Classification System (USCS). Elements of the USCS and other definitions are provided on this and the following pages. Soil descriptions are based on visual-manual procedures (ASTM D2488) and laboratory testing procedures (ASTM D2487), if performed.

STANDARD PENETRATION TEST (SPT)

SPECIFICATIONS

Hammer:

Sampler:

N-Value:

Dry

Moist

Wet

MOISTURE CONTENT TERMS

Modifying (Secondary)

Precedes major constituent

Major

Minor Follows major constituent

1All percentages are by weight of total specimen passing a 3-inch sieve.

2The order of terms is: Modifying Major with Minor.

3Determined based on behavior.

4Determined based on which constituent comprises a larger percentage.

5Whichever is the lesser constituent.

COARSE-GRAINED

SOILS

(less than 50% fines)1

NOTE: Penetration resistances (N-values) shown on boring logs are as recorded in the field and have not been corrected for hammer efficiency, overburden, or other factors.

PARTICLE SIZE DEFINITIONS

RELATIVE DENSITY / CONSISTENCY

Sand or Gravel 4

30% or more coarse-grained:

Sandy or Gravelly 4

More than 12% fine-grained:

Silty or Clayey 3

15% to 30% coarse-grained:

with Sand or with Gravel 4

30% or more total coarse-grained and lesser coarse-grained constituent is 15% or more:

with Sand or with Gravel 5

Very soft Soft Medium stiff Stiff Very stiff Hard

Very loose Loose Medium dense Dense Very dense

RELATIVE

DENSITY

FINE-GRAINED SOILS

(50% or more fines)1

COHESIVE SOILS

< 2 2 - 4 4 - 8

8 - 15 15 - 30

> 30

1Gravel, sand, and fines estimated by mass. Other constituents, such as organics, cobbles, and boulders, estimated by volume.

2Reprinted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be obtained from ASTM International, www.astm.org.

140 pounds with a 30-inch free fall.

Rope on 6- to 10-inch-diam. cathead 2-1/4 rope turns, > 100 rpm

NOTE: If automatic hammers are used, blow counts shown on boring logs should be adjusted to account for efficiency of hammer.

10 to 30 inches long Shoe I.D. = 1.375 inches Barrel I.D. = 1.5 inches Barrel O.D. = 2 inches

Sum blow counts for second and third 6-inch increments.

Refusal: 50 blows for 6 inches or less; 10 blows for 0 inches.

RELATIVE

CONSISTENCY

N, SPT,

BLOWS/FT.

5% to 12% fine-grained:

with Silt or with Clay 3

15% or more of a second coarse-grained constituent:

with Sand or with Gravel 5

< 5%

5 to 10%

15 to 25%

30 to 45%

50 to 100%

Surface Cement Seal

Asphalt or Cap

Slough

Inclinometer or Non-perforated Casing

Vibrating Wire Piezometer

N, SPT,

BLOWS/FT.

< 4 4 - 10

10 - 30 30 - 50

> 50

DESCRIPTION

< #200 (0.075 mm = 0.003 in.)

#200 to #40 (0.075 to 0.4 mm; 0.003 to 0.02 in.)

#40 to #10 (0.4 to 2 mm; 0.02 to 0.08 in.)

#10 to #4 (2 to 4.75 mm; 0.08 to 0.187 in.)

SIEVE NUMBER AND/OR APPROXIMATE SIZE

#4 to 3/4 in. (4.75 to 19 mm; 0.187 to 0.75 in.)

3/4 to 3 in. (19 to 76 mm)

3 to 12 in. (76 to 305 mm)

> 12 in. (305 mm)

Fine Coarse

Fine Medium Coarse

BOULDERS

SOIL CLASSIFICATION

AND LOG KEY

_B O

R

IN

G _C

LA

S

S

-1 -0

-0

.G P

J S

W N

E W

.G D

T

/2

/2

Tuolumne Meadows Parking Tuolumne County, California

July 2020

GC

SC

Inorganic

Organic

(more than 50% of coarse fraction retained on No. 4 sieve)

MAJOR DIVISIONS GROUP/GRAPHIC

SYMBOL

CH

OH

ML

CL

TYPICAL IDENTIFICATIONS

Gravel

Sand

Silty Sand; Silty Sand with Gravel

Clayey Sand; Clayey Sand with Gravel

Clayey Gravel; Clayey Gravel with Sand

Sheet 2 of 3

Gravels

Primarily organic matter, dark in color, and organic odor

SW

(more than 12% fines)

Silts and Clays

Silts and Clays

(more than 50% retained on No.

200 sieve)

(50% or more of coarse fraction passes the No. 4 sieve)

(liquid limit less than 50)

(liquid limit 50 or more)

Organic

Inorganic

FINE-GRAINED

SOILS

SM

Sands

Silty or Clayey Gravel

Silt; Silt with Sand or Gravel; Sandy or Gravelly Silt

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

HIGHLY-

ORGANIC SOILS

COARSE-

GRAINED

SOILS

GW

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

(less than 5% fines)

PT

(more than 12% fines)

MH

SP

GP

GM

Silty or Clayey Sand

Silty Gravel; Silty Gravel with Sand

(50% or more passes the No. 200 sieve) Elastic Silt; Elastic Silt with Sand or Gravel; Sandy or Gravelly Elastic Silt

Fat Clay; Fat Clay with Sand or Gravel;

Sandy or Gravelly Fat Clay

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

Poorly Graded Sand; Poorly Graded Sand with Gravel

Well-Graded Sand; Well-Graded Sand with Gravel

Well-Graded Gravel; Well-Graded Gravel with Sand

Poorly Graded Gravel; Poorly Graded Gravel with Sand

Lean Clay; Lean Clay with Sand or Gravel; Sandy or Gravelly Lean Clay

Peat or other highly organic soils (see

ASTM D4427)

FIG. A-1

OL

(less than 5% fines)

NOTES

1. Dual symbols (symbols separated by a hyphen, i.e., SP-SM, Sand with

Silt) are used for soils with between 5% and 12% fines or when the liquid limit and plasticity index values plot in the CL-ML area of the plasticity chart. Graphics shown on the logs for these soil types are a combination of the two graphic symbols (e.g., SP and SM).

2. Borderline symbols (symbols separated by a slash, i.e., CL/ML, Lean Clay to Silt; SP-SM/SM, Sand with Silt to Silty Sand) indicate that the soil properties are close to the defining boundary between two groups.

SOIL CLASSIFICATION

AND LOG KEY

_B O

R

IN

G _C

LA

S

S

-1…